Program to find sum of two numbers using "functions"

#include<iostream.h>
#include<conio.h>
void sum(int a,int b);
void main()
{
clrscr();
int a,b;
cout<<"enter 2 vaues";
cin>>a>>b;
sum(a,b);
getch();
}
void sum(int a,int b)
 {
  int sum=0;
  sum=a+b;
  cout<<"sum is"<<sum;
 }